Fibrous covering for elastic thread



July l, 1958 c. c. sMrrH 2,840,882

FIBROUS COVERING FOR ELASTIC THREAD Original Filed Deo. '12. `19511 46gi INVENToR.

144.2 y ww le@ f5 475 26M \\f) u 465 l l /V nited States Patent OFIBRoUs CoVERlNG Fon ELASTIC THREAD Charles C. Smith, Providence R. I.,assigner to Darlington Fabrics Corporation, New York, N. Y., acorporation of Delaware Original application December 12, 1951, SerialNo. 261,231, now Patent No. 2,733,179, dated January 31, 1956. Dividedand this application June 7, 1955, Serial No. 513,773

15 Claims. (Cl. 28-81) This invention relates to covered rubber elasticthread. As contrasted with customary prior practice wherein a rubberelastic core thread is encased in a helical wrapping or wrappings oftextile yarn, the present invention provides a covered elastic threadwherein the covering or jacket consists of a multitude of independentbers or laments arranged substantially parallel to each other withouttwist and extending lengthwise of the core to which each ber or filamentis attached at two or more spaced points in its length so as to provide,between adjacent points of attachment, a free length of the ber whichforms a bight or loop, the projecting bights or loops collectivelyforming a soft jacket or covering which is longitudinally stretchablewith the core.

Objects of the invention are to provide a covered elastic thread whichis soft to the hand, so that it may be worn next to the human bodywithout harsh chang of the delicate body tissues; to provide a series ofsoftly enclosed air cells adapted to absorb body exudation, and toprovide for heat or cold insulation; to provide a core with softparallelized covering bers, free at certain intervals, and to permit thegarment made from the thread to accommodate itself to minute bodymovements, without excessive sliding; and other objects which willbecome clear and evident as the specication of the selected embodimentproceeds.

In contradistinction to customary prior practice, the present inventionprovides for covering the elastic core with parallel bers such, forexample, as are obtained by carding, combing or drawing staple lengthbers such as cotton, wool, rayon, nylon or the like, or by cuttingsynthetic laments into staple lengths, or with independent, continuoussynthetic laments which have not been twisted together and which are, inthis form, known in the trade as toW.

Any length of ber, or a blend of various ber lengths or continuouslaments may be employed in the covering operation, as may be desired orconvenient.

According to a preferred embodiment of the invention a continuous orunbroken layer of substanti-ally parallel bers, either staple orcontinuous, is anchored at intervals to the elastic core. i

However, the bers employed should be longer than flock bers and, infact, lthe majority of the bers should be long enough to be attached tothe core at two points, at least, separated from one another by apredetermined distance so as to permit the fibers, when the thread isrelaxed after covering, to form bends or bights projecting from thecore, such bends or bights being shaped, for example, more or less likethe Greek letter omega. These projecting bights or bends collectivelyform a soft, continuous covering or jacket for the core.

By staple fibers is meant natural bers, for example, like cotton, inwhich there is considerable variation in ber length. For example, inwhat is known as 1%; inch American cotton, the ber length will vary from2,840,882 Patented July l, i958 ICC 2 about 1/16 of an inch up to about2 inches, with only about 35% of the bers having a length of lli/16inches.

Short fibers, say about 1A inch or shorter, are sometimes known asilock, particularly when they have been separated, as by combing forexample, from the longer bers.

Synthetic staple bers may also have considerable length variation in theber length array. However, as a general rule, the manufactured staplebers are more uniform in length than the natural staple bers.

For some products, a substantially uniform length staple is desired,while in some other cases a substantial variation in ber length willresult in the optimum product. The ratio of length to diameter of thebers should be very substantial. In staple bers, it is preferable to uselengths of about from say 65 to 25,000 times the diameter of the ber.When continuous laments are used, the length to diameter ratio is almostinnite.

A single relatively short staple ber will form but a few omega-likeloops, for instance only one, while a longer staple ber or a continuouslament may form a larger number of loops, depending on the length of thefiber and the size of the loop.

Sin-ce the ber lengths are not always, and in fact, se1- dom are exactmultiples of the lengths necessary to form a single bight or loop, freeends of many of the bers will project, being interspersed among theloops, and will impart -something of a velvet or flocked effect to thecovering.

In the process of manufacture the core (round, square or of any otherconvenient cross-sectional shape) is rst flattened and simultaneouslytensioned to elongate it to the desired degree. Then while the core istensioned, a series of properly spaced, transverse or diagonal lines areprinted on diametrically opposite sides of the elongated core while thelatter is flattened to form a thin ribbon. The printing fluid is of anelastic and adhesive nature and the parallel bers are pressed into theprinted lines so that on curing, the bers become permanently fastened tothe core at the printed lines while being free from the core betweenadjacent printed lines. When the covered core is relaxed the freeportions of the covering bers project out from the core to form thebights or loops above mentioned, successive bights of a given berlongitudinally of the thread normally substantially contacting.

In accordance with the present invention, the possible elongation of thecovered yarn is entirely independent of the presence or absence of thepre-stresses in the core. In the prior art product the elongation of thecovered yarn is directly related to and is a function of the prestressesin the core. l

In prior practice, wherein the core is covered with a helical wrapping,the core is always pre-stressed to elongate it to a predeterminedpercentage of its maximum safe elongation (elongation to the elasticlimit) while the wrapping is being applied. From its normal relaxedcondition, the covered yarn is only capable of elongation in response toa load greater than that necessary to stretch the core to saidpredetermined percentage elongation and furthermore, since the core, inthe relaxed yarn, is held under radial compression, the relaxed yarn issti and has aharsh feel.

For example, in the prior art, a spirally wound core, for example, thebase core, may be elongated to about its maximum, consistent withsafety, and a number of `spirally wound covering coils Vwound tight onthe eloni prior art, the elastic core has a maximum safe elongation of600%, and a 150% elongation is desired in the covered product, then sucha number of covering convolutions is wound on the elongated core as topermit it to recover only 150% out of the 600% elongation. In such casethe elastic core is longitudinally pre-stressed at 450% and preventedfrom further contraction by the convolutions wound thereon.

According to the present invention the core of the relaxed covered yarnmay have any desired elongation from zero to the maximum safeelongation. The covered yarn may be made to begin to respond instretching to any load which would stretch the uncovered core or tobegin to stretch in response to the application of any predeterminedgreater load up to that which would produce maximum elongation, andcorrelatively, to contract, after extension, to any predeterminedpercentage of its maximum elongation. Moreover, since in the relaxedcover yarn the core is not under radial compression, the yarn is verypliable and has a soft, pleasant feel.

In the practice of the present invention, the core is widened bycompression while being stretched longitudinally. For specific example,if a resilient core has a safe total cubieal displacement factor equalto the cubical displacement resultant from a 600% longitudinalelongation alone, and it is desired that the covered yarn have alengthwise elongation of 150% and at the same time have a soft feel andgoed pliability, the core may be widened, by transverse compression toprovide 450% of the permissive cubical displacement and simultaneouslystretched longitudinally to provide the remaining 150% of the permissivecubieal displacement. The filaments or fibers are then anchored to thestretched and flattened core by transverse bands of adhesive with suchspacing between adjacent bands as will permit the core to contracttransversely to the equivalent of 450% of the permissive cubicaldisplacement and simultaneously to contract in length the equivalent of150% of the permissive cubical displacement. In such a case, the core ofthe covered yarn will have transverse and 0% longitudinal pre-stress. Inother words, it is fully relaxed. For further example, with properspacing of the fiber anchoring bands during application of the fibers,the relaxed covered yarn may begin to stretch upon application of a verysmall load, but stretch may be limited, by the straightening of thefiber bights, at a point where the core has been stretched only 150% ascompared with a possible 600% stretch of the uncovered core.

Again, with proper spacing of the fiber anchoring bands, the action ofthe bands may be such that in the relaxed thread the core will have apredetermined elongation, for example, 150% of its maximum elongationand thus a substantial load must be applied before the covered yarnbegins to stretch. The stretch is limited, as in the preceding case, byvthe straightening of the fibers, for example, at a point where the corehas extended to 400% of its maximum elongation.

As above suggested, the permissive elongation of the covered core iscontrolled by printing the anchoring lines of adhesive closer or fartherapart or by elongating the flattened ribbon more or less preparatory toprinting. Thus, for example, if a 150% elongation be desired in thefinished product, the attened ribbon is elongated about 150% while beingprinted. desired, then the ribbon is elongated to 400%, while beingprinted. Alternatively, by printing the anchoring lines of adhesive on acore which has been stretched substantially to its elastic limit, with aspacing so dimensioned as to permit a 150% of a 400% recovery in thecompleted thread, there will be produced a pre-stressed core such thatthe thread will have a greater load-carrying capacity before elongationstarts than in the former case, which results in a softer acting thread.Thus any desired elongation may be provided for the finished coY-. eredthread.` It may be noted that the knitting trade If a 400% elongationbe' thereafter will retain that original shape during normal use. Onsuch recovery the covering bers attached to the diametrically oppositefaces of the core, while it was fiat, will be substantially uniformlydistributed, peripherally, about the outer surface of lthe relaxed core,the projecting bights forming a low pitch helix coaxial with the core.

In the accompanying drawings Fig. l is a diagrammatic, vertical sectionillustrating one desirable form of apparatus for use in the practice ofthe invention;

Fig. 2 is a greatly enlarged, fragmentary elevation of a rubber elasticcore thread showing various steps in the process of covering it;

Fig. 3 is a transverse section on the line 3*?) of Fig. 2, illustratinga core of circular normal section;

Fig. 4 is a transverse section through the core as it appears whenflattened preparatory to the application of adhesive;

Fig. 5 is a transverse section illustrating the diagonal, sticky areason one side of the flattened core resultant from the printing operation;

Fig. 6 is a transverse section, substantially on the line 6.-6 of Fig.2, showing the parallel covering fibers partially embedded in the stickyarea on one side of the flattened core, the fibers on the opposite sidebeing free from the core;

Fig. 7 is a transverse section, to very large scale, substantially onthe line 7 7 of Fig. 2, showing the core after the tension has beenpartly relaxed and indicating the uniform peripheral distribution of thecovering fibers puffed out into radial bights or loops;

Fig. 8 is a fragmentary elevation partly in section and to very largescale, showing one of the rows of bights as they appear in the relaxedthread;

Fig. 9 is a greatly enlarged longitudinal, fragmentary section, showingone of the omega-like bights or loops and the way in which it isanchored to the core; and

Fig. 10 is a diagram illustrative of a principle made use of in thepractice of the present invention.

In accordance with the present invention use is made of a phenomenonobserved in the stretching of a rubber elastic thread which isillustrated in Fig. l0. In this view the character T represents arelaxed rubber elastic thread of circular transverse section which ispassed between a pair of rigid rollers R, one of which is shown. Forpurposes of illustration it may be assumed that the rollers R do notturn but that they are spaced apart a distance such that the threadsqueezed between them is widened and flattened so that at this portionits Width exceeds the diameter of the original thread T.

Assuming that initially a length of the thread has been passed betweenthe rollers, for example by turning them, so as to provide a portion T2to which tension may be applied in the direction of the arrow A by aforce IT, and that this tension has been increased until the combinedtransverse and longitudinal displacement of the molecules of the rubber,due to the compression of the thread between the rolls and theapplication of longitudinal tension, substantially equals the cubicdisplacement which would result from the application of stress,longitudinally only, up to the elastic limit of the thread, the threadwill begin to iiow from between the stationary rollers R. Assuming thatthe point K is the point in the thread which was being gripped by therolls at the instant the tension F reached the above intensity, thethread willv emerge from the rolls as a ribbon T1, thepoint K advancingand all ofthe thread between the point K and the rollers R being liat,while all of the thread below the point K will remain of its initialcircular transverse section. If the force F for advancing the thread beapplied by passing the thread through a second pair of rolls R2, drivenat the proper speed, the entire length of thread between the two sets ofrolls, after the point K has passed the rolls R, will be fiat, but asthe thread emerges from between the rolls R2 it will resume its initialcircular section. By the use of this principle, it is possible tosubject a portion of a normally circular thread to a treatment whichordinarily could be applied only to a flat ribbon, but the result ofsuch treatment, as compared to its application to a normally flatribbon, will bemodied when the thread resumes its normal circularsection.

The above principle, that is to say the retention of its liattenedcondition in response to the concomitant application of liatteningpressure and tension, is applicable to rubber elastic threads of anyinitial transverse section and even to the covering of elastic sheetmaterial, on one or both sides, but for most purposes its utility isdirected to its application to threads of initially regular transversesection, that is to say threads of circular or regular polygonalsection, and when hereinafter reference is made to a thread of regulartransverse section such term is intended to apply to threads of anyregular polygonal section and also to threads of circular transversesection.

Referring to Fig. 1, which illustrates a selected mechanical embodimentof means for use in the practice of the invention, a plurality ofcore-supporting spools (three such spools being shown by way of example)are indicated at 20, 20a and 20h, these spools being driven by aconventional uniform surface speed drive mechainism comprising the driverolls 21, 21a and 2lb by means 4of which the relaxed elastic core yarns22, 22a and 22b .are unwound from the spools or supply packages and arefed through guide eyes 23 (only one of which is shown) into the nip of apair of feeding tensioning :means 24, 24. These rolls 24, 24 arepositively driven :at a uniform, peripheral speed and are adjustablysupported in a manner conventional in the art so that any desired spacemay be provided between them at the nip point. Since the means fordriving and adjusting the rolls 24, 24 may be conventional they have notbeen herein illustrated. The nip rolls 24, 24 are of a length such as togrip a substantial number of core threads simultaneously. The eyes 23guide the longitudinally spaced elastic core yarns from the severalsupply packages 20, 20a, 2Gb, etc. so that they enter the nip rolls inspaced, side-by-side relation. Any number of core yarns may be coveredsimultaneously but to facilitate the operation it is preferable to spacethe core yarns so that there are from four to sixteen core yarns perinch of length of the nip of the rolls 24, 24, depending on the size ofthe core yarns.

The core yarns are drawn through the mechanism by a second pair of niprolls 25, 25 spaced a suitable distance from the rolls 24, 24. The rolls25, 25 are driven at a higher peripheral speed than the rolls 24, 24thereby to elongate the core threads to the desired degree within thezone at which the actual covering operation is performed. The desiredelongation may be produced (within the capacity of the elastic material)by adjusting the peripheral speed of the rolls 25, 25 relatively to thatof the rolls 24, 24, any convenient means being provided for adjustingthe speed of either one or both of the pairs of rolls 24, 24 or 25, 25.The linear speed dilierence between the nip rolls 24, 24 and 25, 25shall be such as to provide the necessary balancing tension, on thatportion of the-transversely elongaged core which is located betweentheseV two sets of nip rolls, to prevent the premature recovery of thetransverse displacement. No speed-adjusting mechanism is hereillustrated since 6 such mechanism is well known in the art and may beconventional.

The printing, liber deposit and curing and setting of the adhesiveanchoring material are all performed within the space between the twosets of rolls 24, 24 and 25, 2S and simultaneously at diametricallyopposite sides or faces of the flattened and tensioned elastic core.

Any desired design, including lines, dots, etc., may be printed on thefaces of the core while the latter is flattened by the action of theengraved printing rolls 26, 26 (these rolls being at opposite sides ofthe core). The printing rolls are supplied with suitable printingcompound 27 held in containers 2S, 28 from which it is carried up by thefeed rolls 29, 29 and deposited on the undersides of the engravedprinting rolls 26, 26. This printing compound a type which, when firstapplied, is sticky or tacky which sets when properly treated so as to beretentive of the libers which may be placed in contact with it while inits tacky condition. The adhesive material is also of a nature such thatwhen it has set it is elastic so that it is capable of elongating withthe elastic core without separating from the latter. The excess printingcompound is removed by doctor blades 30, 30 of conventional design. Theprinting rolls 26, 26 and the feed rolls 29, 29 are suitably driven inthe direction indicated by the arrows in Fig. l, by any conventionaltype of drive mechanism, not shown.

The printing rolls 26, 26 are relatively adjustable thereby to permitcontacting of the iiattened core at the printing point and anyappropriate conventional means may be provided for driving and adjustingthe printing rolls.

After the adhesive has been printed onto the core the fibers aredelivered for contact with the printed areas. As here illustrated thefibers or filaments are applied to the core by means of a pair ofendless belts -or blankets 3l. and 3l.2L suitably supported and drivenby rollers 32, 33

and 32a, 332l which may be supported on a frame (not These rolls aremade of wool, felt, fine cotton duck, canvas or similar material towhich the bers will ten-d to cling and so as to be carried thereby, andwhich have a comparatively smooth surface with which to press the fibersinto the printed anchoring places. The fibers for use in making thecovering are supplied as a pair of packages 34 and 343'. These packagesmay be rolls of carded -or combed staple fiber in sliver form or acontinuous filament tow, the constituent fibers or lilaments beingsubstantially parallel. Any other convenient arrangement may be used forsupplying the fibers to the belts 3l and 31a. The fibers are deliveredto the belts 31 and 31a by a set of feed rolls 35 and 36; 35a and 36EL(one pair for each belt), driven in any conventional manner. The belts3i and 31a are provided with pressure plates 37, 37 each located betweencorresponding belt-supporting rollers and each being adapted yieldinglyto bear aaginst the inside run of the corresponding belt so as toprovide the necessary pressure to press the fibers against the stickyareas formed on the core by the printing rolls. These pressure plates 37may be yieldingly urged toward each other in any suitable way, forexample, by springs or weighted levers (not shown).

rEhe pressure plates 37, 37 may be mounted on electrically insulatingstandards (not shown) and electrically grounded (not shown) so as, ineffect, to constitute a tribo-electric magnetic condenser plate,resiliently to hold the fibers onto the belt or blanket.

Such a tribo-electric magnetic condenser plate is fully arrows thesticky areas of the core will pick up all of the bers from the surfacesof the belts which can be embedded inthe adhesive material by thepressure plates 37, 37. Any excess fiber not thus picked up continues tofollow the belts 31 and 31a. The speed `of the feed rollers 35, 36 whenproperly adjusted, is such as to deliver only enough fibers to the beltsto replenish the supply on the latter. Combs 39 and 39a are arranged toeven up the fibers on the belts or blankets 31 and 31a. The linear speedof the printing rolls 26, 26 and the linear speed of the belts orblankets 31 and 31a are so relatively adjusted as to coincide with thelinear speed of the core thread at the particular elongation determinedby the speed difference between the rolls 24, 24 and 25, 25.

After the fibers have been deposited and adhesively attached to thesticky areas of the core thread, the covered thread is drawn through adrying, curing cr vulcanizing device 40 provided with inlet and outletopenings 41 and 42 respectively. If the adhesive employed is such asbecomes set by exposure to a high temperature, the apparatus 40 may beprovided with heating elements 43, 43 of any desired type and adapted todry, cure or vulcanize the printed compound. lf the adhesive material issuch as becames set by exposure to a gaseous or other uid medium, thenthe device 40 may be provided with means for exposing the covered threadto such a uid medium on its way through the device 40. Obviously if thesticky material be of a self-curing nature, such that it sets quicklyupon exposure to the air, or if it be a thermoplastic material whichsets upon cooling, the device 40 may be dispensed with.

The covered and cured elastic thread passes between the rolls 25, 25 andas soon as the tension is relaxed it resumes its original cross-sectionshape which it had before it entered the rolls 24, 24. Thus if thenormal section of the elastic thread was round before entering the rolls24, 24, it will resume its round shape after leaving the rolls 25, 2S.Likewise a square thread will become square, a triangular thread willbecome triangular and so on, it being noted that the flattening actionwhich the core undergoes during the operation of attaching the fibersresults in no permanent deformation, assuming, of course, that theelastic thread has such a normal elasticity as to cause it to resume itsoriginal cross-sectional shape. However, as has been stated, thedischarge nip rolls 25, 25 have a higher `peripheral speed than thefeeding nip rolls 24, 24 so that the portion of the core body, locatedbetween these pairs of rollers, will be under the desired longitudinalstress which shall be of such magnitude as to balance the transversestresses and thus hold the core body in a transversely attenuatedcondition.

The covered and relaxed threads 44, 44a and 441 are wound on suitablecores 45, 45" and 45b driven by drums 46, 46a and 46h respectively, at auniform surface speed in a conventional manner, the drums turning in thedirection indicated by the arrows. Distributing lingers 47, 47a and 47may be provided for distributing the completed elastic threadlongitudinally of the cores, these distributing fingers being moved backand forth in a conventional way.

The various parts of the apparatus are supported on appropriate framemembers (not shown) and the driving means for the various rotating partsmay comprise conventional gears, belts, chains or the like which receivetheir motion from a suitable power source (not shown).

Referring to Fig. 2, one of the elastic core threads is shown to greatlyenlarged scale. In the upper part of the figure the core thread 22 isshown in its normal or relaxed form, this core being of round orcircular section, as shown at Fig. 3. As the core thread passes betweenthe rolls 24, 24 and later through the rolls 25, 25 it is flattened bythe rolls 24, 24 to form a thin ribbon and by virtue of the tensioningeffect of the rolls 25, 2S this flattened core will 4retain itsribbon-like cross section throughout the portion intervening between therolls 24, 24 'and '25, 25, as illustrated, for example, at the centralpart of Fig. 2, and in the transverse sections of Figs. 4, 5 and 6. Itis preferred to flatten the thread sufficiently to produce a 10 to 50%transverse enlargement in the width of the flattened section, ascompared with the normal relaxed diameter of the thread, while at thesame time, by the tensioning action of the rolls 24, 24 and 25, 25 theflattened portion is elongated to result in a reduction in thickness of50 to 90% of the original diameter of the relaxed cylindrical thread.For example, if a round thread having a relaxed diameter of 0.020 incl-iis used, ir may be so attened and tensioned that the flattened portionof the thread will be about 0.022 inch wide and about 0.002 inch thickat the point at which the adhesive is printed on.

In printing this attened ribbon-like thread the socalled lake printingprocess may be used. According to this process the printing rolls haveengraved cavities which become filled with the printing compound, theexcess being removed by a doctor blade. As the printing rolls pressagainst the flattened thread these small lakes of printing compound willadhere to the face of the attened thread and will be pulled out of thecavity in the rolls, thus depositing a predetermined measured quantityof compound on the thread. As suggested, the printing compound is suchas to produce sticky areas on the core thread. Usually the printingcompound will be adhesive when applied and capable of setting whensubjected to appropriate treatment. In the particular illustration shownin Fig. 2, the flat surfaces of the core thread have been printed withdiagonal bands 51 on one side and 52 on the opposite side. The printedsection, as a whole, is designated by the numeral 53. The diagonal lines51 may be so arranged as to form a substantially unbroken helix when theelastic thread is subsequently relaxed. Obviously any other design maybe printed on the core, if preferred.

The covering fibers stick to the printed areas as the core passesbetween -the belts 31 and 31a. These bers indicated at 54 (Figs. 2 and6) are straight and substantially parallel with each other and extendlongitudinally of the elastic core thread. The initial spacing ofadjacent sticky bands 51 or 52 determines the height of the omega-likebights or loops which the covering bers form when the thread is relaxed;that is if the initial distance between adjacent bands 51 or 52 is madelong, the omegalike loops will be high, that is to say they will projecta substantial distance from the core when the latter is relaxed. If thedistance between adjacent bands 51 is short, the loops will be low; thusthe thickness of the jacket or covering material may be controlled asdcsired. For purposes of illustration a relaxed thread having a diameterof 0.020 inch may be provided with bands 51 or 52 spaced from 0.015 to0.02 inch apart. Such spacing will produce a loop height ofapproximately 0.005 to 0.007 inch measured radially out from theperiphery of the core. Such omega-like bights or loops are indicated at56 on the relaxed core (Figs. 2, 7, 8 and 9).

Since the anchoring bands l51 and 52 are printed on the diametricallyopposite, attened faces of the core, a small gap l57 (Fig. 6) will beleft near each edge of the attened section. As a rule these gaps are ofa lesser thickness than that of the flattened core. By reducing theviscosity of the printing compound so that it flows around the edges ofthe flattened core these gaps may be eliminated. However for ornamentalpurposes such gaps may be retained or even made purposely wider.

Referring to Fig. 9, one of the omega-like loops 56 and also parts oftwo adjacent yprinted bands 51 are shown in a part of the relaxed core46. The space between adjacent bands 51 (as shown in Fig. 2) hasshortened as the core contracted so that the bands S1 in Fig. 9 are muchcloser together than those in Fig. 2. Those portions 54X of vthe berwhich have become embedded in the adjacent bands 51 remain substantiallyparallel to 9 the axis of the core while the intervening loose portionof the ber buckles out to form the loop 56 (Fig. 9). This projectingloop with the portions 54X which may be referred to as the legs of theloop, forms a gure suggestive of the Greek letter omega. However, it maybe observed that if the spacing of the bands 51, as applied to thetensioned core, is substantially less than that illustrated in Fig. 2,the resultant loops or bights, when the core is relaxed, may be of ashape less closely resembling the Greek letter omega and, in fact, maymore nearly approach the shape of the letter U.

In passing through the curing device 40 the leg or foot portions 54X ofthe loops are permanently anchored to the core by the setting of theadhesive. The projecting portions 56 of the loops collectively form theperipheral surface of the core cover or jacket in the completed thread,it being noted that the parallel bers are quite close togetherperipherally of the thread and that successive bights of any given bermay be very close together and substantially touch when the core isfully relaxed.

Since the bands 51 of rubber adhesive are applied to and cured (and thusin fully relaxed condition) while the core is tensioned, the relief ofcore-tensioning stress tends to compress each band axially of the coreand thus, collectively, the resistance of the bands 51 to suchcompression may limit contraction of the core to a predetermined amount,dependent upon the initial spacing and width of the bands 51.

When the covered thread prepared as above described is elongated duringuse, each of the loops 56 will, at full extension of the thread, becomea straight continuation of its leg orV foot portion 54X. If the threadis stretched to any substantial further degree the bers will rupture andthe core will thereafter break. The extensibility of the complete threadmay be so calculated that the bers 54 and the core 46 will rupturesimultaneously or practically so. For most uses such a simultaneousbreak of the covering and core is desirable. However for certain specicpurposes it may be desirable to provide a construction such that thefibers 54 will break while the core 46 is still capable of substantialfurther elongation before reaching its elastic limit. n the other hand,it may sometimes be desirable to construct the covered thread so thatthe core 46 will rupture rst and the ber covering will rupture only onfurther elongation. However, the `greatest tensile strength of a givencovered thread is obtained when the rupture of the core and covering issubstantially simultaneous.

The improved covered thread, according to the present invention, has avery soft, lofty covering or jacket providing a wholly diiferent feelfrom that -of a thread covered by the usual spiral windings of the priorart. Furthermore, the improved thread of the present invention iscapable of elongation to a very substantial degree without exposing theycore whereas threads covered with spiral coverings, according to usualprior practice, can only be elongated to a limited extent before thecore thread is exposed. Moreover, by the present procedure the core isadequately covered by the use of a `substantially less amount of fibrouscovering material than is necessary when other prior methods of coveringare employed.

The term rubber elastic is herein employed as a convenient expression todenote a material having the elastic stretch characteristics similar tothose ofl natural India rubber and is to be understood as inclusive ofall such other materials, among them the synthetic rubbers, as havesimilar physical characteristics.

While as herein specically described the ber is attached to the elasticthread by the use of adhesive, usually a material different from that ofthe thread, it is contemplated as within the scope of the invention,particularly when the elastic thread is of a synthetic material, thatthe adhesion of the ber may be obtained by causing the stance, by theuse of a volatile solvent or by the application of heat in anyconvenient way.

While a desirable embodiment of the invention has herein beenillustrated and described by way of example it is to be understood thatthe invention is Ibroadly inclusive of any and all modifications fallingwithin the scope of the appended claims.

This application is a division of my copending application for FibrousCovering for Elastic Thread and Method of Producing It, Serial No.261,231, led December 12, 1951, now Patent No. 2,733,179.

I claim:

l. A relaxed rubber elastic core thread and jacket encasing andsubstantially concealing the thread, the thread and jacket beingstretchable when the thread is subjected to longitudinal tension, thejacket being attached at longitudinally spaced intervals to the thread,and having a plurality of projecting brous bights between each adjacentpair of points of attachment.

2. A relaxed rubber elastic core thread and jacket encasing the thread,the thread and jacket being stretchable to substantially the samedegree, thejacket comprising a substantially uninterrupted row of brousloops which collectively form a soft cushion-like surface.

3. In c ombination with a single bare, radially uncompressed rubberelastic core thread, a multitude of elongate bers disposed about theperipheral surface of the core, side by side, and means adhesivelyattaching each ber to the core at spaced points in its length and withportions between adjacent points of attachment projecting as openbights.

4. In combination with a single bare rubber elastic core thread, saidcore being radially uncompressed so as to be free to relax completely inthe absence of stress applied longitudinally thereto, a multitude ofbers, each ber forming projecting bights and adhesive attaching each berto the core at points intervening between adjacent bights.

5. In combination with a relaxed rubber elastic core thread, a multitudeof open bights of brous -material collectively substantially concealingthe core thread, the legs of each bight being permanently attached tothe surface of the thread.

6. In combination with a bare rubber elastic core thread, said corebeing radially uncompressed, substantially parallel bers extendinglongitudinally of the thread and disposed peripherally, side by side, onthe bare surface of the core thread, and adhesive attaching each ber tothe core thread at points spaced lengthwise of the core thread, thepoints of attachment deiining a helix about the periphery of the corethread, each ber being free from the core thread between adjacent turnsof the helix.

7. In combination with a relaxed rubber elastic core thread, a multitudeof omega-shaped bights of brous material, and adhesive attaching thelegs of each bight to the thread.

8. In combination with a relaxed rubber elastic core thread, a multitudeof omega-shaped bights of fibrous material, the legs of each bightextending parallel to the axis of the core -thread and being permanentlyattached to the thread, the bights collectively forming a helix of lowpitch coaxial with the thread.

9. In combination with a relaxed rubber elastic core thread, alongitudinally extensible jacket of textile ber 'encasing andsubstantially concealing the thread, said jacket comprising a multitudeof independent, substantially parallel bers of staple or greater length,and means 'attaching each ber at spaced points in its length to thethread, the bers forming loose bights intermediate their points ofattachment whereby elongation of the thread, when subjected to tension,is permitted.

l0. In combination with a relaxed rubber elastic core thread, amultitude of laments of synthetic textile material extending lengthwiseof the thread, each lament thread itself to become temporarily adhesiveas, for informing a plurality of omega-shaped bights, means pereachbight being disposed in a substantially radial plane,`

the bights collectively forming a jacket which substany tially coversthe thread but which does not substantially limit the elongation of thethread.

1l. In combination with a single rubber elastic core thread,substantially parallel bers extending longitudinally of the thread,means attaching each fiber to the thread at points spaced lengthwise ofthe thread, each fiber forming a radially projecting bight betweenadjacent points of attachment, the bights collectively forminga helix oflow pitch extending around the thread and substantially concealing thethread when the latter is relaxed.

12. In combination with a single rubber elastic core thread,substantially parallel fibers extending longitudinally of the thread,means attaching each ber to the thread at points spaced lengthwise ofthe thread, each fiber projecting as a loose loop between adjacentpoints of attachment, the points of attachment being so close togetherwhen the thread is relaxed that adjacent loops of the same bersubstantially contract.

13. In combination with a relaxed rubber elastic core thread, a jacketof textile ber encasing and substantially concealing the thread, saidjacket comprising a multitude of independent bers of staple or greaterlength, each liber being attached at spaced points in its length to thethread and having a projecting bight intermediate its points ofattachment, the lengths of said bights being such as to permitsubstantial elongation of the elastic thread but to limit suchelongation to a predetermined fraction of its normal possible stretch.

14. In combination with a relaxed rubber elastic core thread, a jacketof textile ber encasing and substantially concealing the thread, saidjacket comprising a multitude of independent fibers of staple or greaterlength, each ber being attached at spaced points in its length to thethread and having a projecting bight intermediate its points ofattachment, the bights disappearing and thetibers becoming substantiallystraight when the core thread is stretched substantially to its elasticlimit.

15. In combination with a single rubber elastic core thread,substantially parallel fibers extending longitudinally of the thread,means attaching each ber to the thread at points spaced lengthwise ofthethread, each fiber projecting as a bight between adjacent points ofattachment, the length of ber between adjacent points of attachmentsubstantially equalling the possible separation of adjacent points ofattachment by the elongation of the thread within its elastic limitswhereby the maximum strength of the covered core substantially equalsthe sum of the tensile strength of the uncovered core and the collectivestrength of the fibers.

References Cited in the le of this patent UNITED STATES PATENTS2,048,360 Spanel et al. n July 2l, 1936 2,072,775 Smith et al Mar. 2,1937 2,213,290 Rowe Sept. 3, 1940 2,424,743 Davis July 29, 19472,705,687 Petterson et al. Apr. 5, 1955 2,733,179 Smith Jan. 31, 1956FOREIGN PATENTS 475,399 Great Britain Nov. 18, 1937 661,530 GreatBritain Nov. 21, 1951

